Dual carburetor control system



E. OLSON ET AL DUAI.. CARBURETOR CONTROL SYSTEM Jan. 13, 1959 5 Sheets-Sheet 1 Filed Sept. 9, 1955 w mb 1 INVENTORS 1. M52 045 ON 3 DONALD D. STOLTMAA aw' mmza.

ATTOENE Y Jan. 13, 1959 I E. OLSQN ETAL DUAL CARBURETOR CONTROL SYSTEM Filed Sept. 9, 195:;

3 Sheets-Sheet 2 INVENTORS E L M512 0L.so/v y 001mm .1). STOLTMAN ATTORNEX Jan. 13, 1959 E; oLsoN ETAL DUAL CARBURETOR CONTROL SYSTEM Filed Sept. 9, '1955 3 Sheets-Sheet 3 mmvroxs ELMER OLso/v 3y DONALD D. SToLTM N ATTORNEY Unite States DUAL CARBURETOR CONTROL SYSTEM Elmer Olson and Donald D. Stoltman, Rochester, N. Y., assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September 9, 1955, Serial No. 533,492 2 Claims. (Cl. 261-23) This invention relates generally to charge forming devices, and particularly to a dual carburetor control system for internal combusion engines.

It has been recognized, heretofore, that a carburetor having a single induction passage for each manifold of an engine with two intake manifolds, is unable to satisfactorily meet all of the requirements of such an engine throughout its intended operating range. To overcome this difficulty, multibarrel carburetors have been developed wherein a primary set of induction passages supply the fuel mixture for low and medium speed operation, and a secondary set of induction passages supplies additional mixture for high speed operation. In a system of the aforedescribed type, one primary and one secondary induction passage communicate with each intake manifold. At the present time, some vehicles are equipped with two multibarrel carburetors, since one multibarrel carburetor is incapable of supplying a sufficient volume of fuel mixture for maximum power output at high engine speeds. This invention relates we control system for the throttle valves of the secondary induction passages of two multibarrel carburetors. Accordingly, among our objects are the provision of means for effecting synchronized operation of the secondary throttle valves in a pair of mult'ibarrel carburetors; the further provision of motor means for controlling the secondary throttle valves of a multibarrel carburetor; and the still further provision of plural motor means for controlling the secondary throttle valves of a pair of multibarrel carburetors.

The aforementioned and other objects are accomplished in the present invention by operatively interconnecting the secondary throttle valves of a pair of multi-barrel carburetors for simultaneous actuation. The present invention eliminates the possibility of the secondary throttle valves of one carburetor remaining closed when the secondary throttle valves of the other carburetor are open. Specifically, the control system includes means, such as a link, for interconnecting the primary throttle valves of both carburetors so as to elfect simultaneous manual operation thereof. In one embodiment, one of the carburetors includes a motorresponsive to the vacuum in primary induction passage of one carburetor for controlling the secondary throttle valves thereof, and link means interconnecting the secondary throttle valves of both carburetors.

In a second embodiment, both carburetors include motors for controlling their secondary throttle valves, both motors being responsive to the vacuum in the primary induction passage of one carburetor. In a third embodiment, each carburetor includes a motor for controlling the secondary throttle valves thereof, each motor being responsive to the vacuum in the primary induction passage of its respective carburetor and link means interconnecting the secondary throttle valves of both carburetors. In a fourth embodiment, each carburetor includes a motor responsive to the vacuum in the primary 4 2,868,520 Patented Jan. 13, 19.59

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induction passage of one carburetor and link means inter connecting the throttle valves of both carburetors.

In all embodiments, the vacuum controlled motor comprises .a casing having disposed therein a diaphragm which divides the casing into the vacuum chamber and an an chamber. The vacuum chamber is connected to a vacuum conduit, and the diaphragm ,is connected .to one end of a plunger. The other end of the plunger is connected to a secondary throttle shaft arm. The arm is formed with two lever extensions, one of which is connected to the vacuum motorplunger, or rod, and the: other .of which is connected to one endof a coil spring. The other end of the coil spring is suitably connected to the motor casing. The effective length of lever extension through which the spring acts varies with the position of the secondary throttle valve shaft. More particularly, the effective lever length, or the distance between the axis of the shaft and the axis of the coil spring, shortens as the secondary throttle valves move towards the open position so that as soon as the vacuum motor overcomes the force of the spring at closed throttle position, the secondary throttle valves will move quickly towards the fully open position. Thereafter, the secondary throttle valves will assume a position in accordance with the primary induction vacuum, since as the secondary valves open, the actuating torque (product of vacuum and diaphragm area) decreases while the closing torque (product of lever arm and spring force) decreases. When the opposing torques arein equilibrium, the secondary valves will remain stationary.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown and wherein similar reference characters denote similar parts throughout the several views.

In the drawings:

Fig. l is a fragmentary View of an engine depicting one embodiment of the present invention.

Fig. 2 is a schematic illustration of the manifold con struction and dual carburetor installation.

Fig. 3 is a fragmentary view, partly in section and partly in elevation, depicting one embodiment of the present invention.

Fig. 4 is a fragmentary view, partly in section and partly in elevation, depicting operation of the motor means for controlling the secondary throttle valves.

Fig. 5 is a fragmentary view, in elevation, of the second embodiment of the present invention.

Fig. 6 is a fragmentary view, in elevation, of a third embodiment of the present invention.

Fig. 7 is a fragmentary view, in elevation, of a fourth embodiment of the present invention.

8 is a graph depicting the manner in which the actuating vacuum varies with the position of the second ary throttle valves when the primary throttle valves are fully open.

With particular reference to Figs. 1 and 2, the present invention is shown in combination with an internal combustion engine having a V-type block, the engine block being indicated by the numeral 10. The engine includes two intake manifolds 11 and 12, one intake manifold supplying fuel mixture to cylinders 31, 33, 35 and .37, and the other intake manifold supplying fuel mixture to cylinders 32, 34,36 and 38. A rear carburetor 13 communicates with the manifolds 11 and 12, and the front carburetor 14 also communicates with the manifolds l1 and 12.. Both carburetors 1.3 and 14 are of the multibarrel type and, thus, include a pair of primary induction passages and a pair of secondary induction passages. Thus, the rear carburetor 13 includes primary induction passages 15 and secondary induction passages 17, while The primary induction passages of the carburetors 13 and 14 contain main venturis 19 and 21 respectively, as well as thermostatically-controlled, unbalanced choke valves 21 and 22, respectively, which regulate the admission of air into the primary induction passages and 16. The primary induction passages 15 and 16 also contain primary throttle valves 23 and 24, respectively, mounted on shafts 25 and 26, respectively. The primary throttle valve shafts 25 and 26 have connected thereto levers 27 and 28, the levers 27 and 28 being interconnected by a link 29. The lever 27 of the rear carburetor 13 is also connected to one end of a link 30, the other end of which is operatively connected to a manually operable accelerator pedal, not shown. Thus, it is apparent that the primary throttle valves of both the rear and front carburetors 13 and 14 are interconnected for synchronized manual actuation. The secondary induction passages 17 and 18 of the carburetors 13 and 14 have disposed therein secondary throttle valves 39 and 40, respectively, which are connected to shafts 41 and 42, respectively. One primary induction passage and one secondary induction passage of each carburetor communicates with each of the manifolds 11 and 12, as depicted in Fig. 2.

The construction of multi-barrel carburetors 13 and 14, except for the novel secondary throttle valve actuating mechanism, may be of the type disclosed in copending application, Serial No. 264,136, filed December 29, 1951, in the name of Elmer Olson and Lawrence C. Dermond and assigned to the assignee of this invention.

In some commercial four-barrel carburetors, the secondary throttle valves are controlled by motor means responsive to vacuum at the main venturi of one or both of the primary induction passages. When two of these carburetors are employed on an engine, it has been noted that the secondary throttle valves of one carburetor may open first and so reduce the vacuum at the main venturi in the primary inductio-n'passages of the other carburetor to a point that the vacuum is inadequate to actuate the motor controlling the secondary throttle valves of the other carburetor. If this should occur, the secondary throttle valves of the other carburetor will remain closed and, thus, the beneficial effects sought to be accomplished with two multi-barrel carburetors will not be realized. In other words, since in a V-eight engine, both intake manifolds 11 and 12 communicate with both carburetors, when the secondary throttle valves of either carburetor 13 or carburetor 14 open, the vacuum at the venturi in themaln induction passages of both carburetors will diminish appreciably, as depicted in the graph in Fig. 8. The vacuum will be sufiicient at the primary main venturis to maintain the secondary throttle valves which have opened in their open positions since the vacuum required to initiate opening movement of the secondary throttle valves is considerably higher than that required to maintain the secondary throttle valves in a wide open position, as will be pointed out with greater particularity hereinafter.

The present invention obviates the aforementioned difiiculty by assuring that the secondary throttle valves of both carburetors will be actuated simultaneously. In the first embodiment, as depicted in Figs. '1 and 3, the secondary throttle valve shaft 42 of the front carburetor 14 has attached thereto an actuating arm 46. The shaft 41 of the rear carburetor 13 has attached thereto an arm 45 with two lever extensions 47 and 49. The lever extension 47 is connected by a link 51 with the arm 46 of the front carburetor 14. Thus, the secondary throttle valves of both the front and rear carburetors are operatively connected for synchronous movement.

The arm 45 of the rear carburetor 13 is also connected to one end of a diaphragm actuated rod 53 constituting a component of vacuum motor 75, the other end of which is attached to a flexible diaphragm 55. The diaphragm 55 is disposed in a two-part casing 57 and divides the easing into a vacuum chamber 59 and an air chamber 61. The air chamber communicates with atmosphere through a fitting 63, the rod 53 extending through the fitting. The casing 57 is suitably connected to the carburetor body and includes a bracket to which one end of a coil spring 67 is attached. The other end of the coil spring 67 is operatively connected to the lever extension 49 of the arm 45 through a link 69. The spring 67 constitutes a return spring for the secondary throttle valves, and normally maintains the secondary throttle valves of the front carburetor in the closed position. Since the secondary throttle valves of the front and rear carburetors are interconnected by link 51, the spring 67 will also maintain the secondary throttle valves of the front carburetor in the closed position The vacuum chamber 59 of the casing 57 is connected by a conduit 71 with the main venturi 19 of the primary induction passages 15 of the rear carburetor 13.

One of the features of the present invention resides in the unique variable torque arm connection between the spring 67 and the secondary throttle valve shaft 41. As can be seen by comparing Figs. 3 and 4, when the arm 45 rotates in the clockwise direction, the distance between the axis of the spring 67 and the axis of the shaft 41 along a line perpendicular to the axis of the spring 67 and radial to shaft 41 decreases from the distance X in Fig. 3 to the distance Y in Fig. 4. In other words, as the secondary throttle valves 39 of the carburetor 13 move towards the open position, the lever arm through which spring 67 opposes this movement gradually decreases from the maximum value X to the minimum value Y. At the same time, the force of the spring increases,'due to elongation. The lever arm arrangement is such that the product of the spring force and the effective lever arm length gradually reduces during movement of the secondary throttle valves from the closed position to the Wide open position. Thus, the secondary throttle valve position is determined by the vacuum at the main venturi of the primary induction passage means. When the secondary throttle valves 39 are wide open, the lever arm through which the spring 67 acts is at a minimum. Hence, it is apparent that the vacuum required to main tain the secondary throttle valves in an open position will be considerably less than the vacuum required to initiate movement thereof from the closed position.

Operation of the first embodiment is as follows. When the vehicle operator depresses the accelerator pedal, not shown, the throttle valves in both primary induction passages of both carburetors Will be simultaneously moved towards the fully open position. When the vacuum at the main venturi 19 of the primary induction passage 15 of the carburetor 13 reaches a predetermined value, due to air flow therethrough, the diaphragm motor will be actuated by the pressure differential on opposite sides of the diaphragm 55 whereby the diaphragm will move from the position of Fig. 3 towards the position of Fig. 4 so as to open the secondary throttle valves 39 of the carburetor 13. Inasmuch as the secondary throttle valves 40 of the carburetor 14 are interconnected through arm 46 and link 51 with the arm 45, the secondary throttle valves 40 also will be moved towards the open position simultaneously with secondary throttle valves 39. In this manner, the volume of fuel mixture required for-maximum power output at high engine speed will be supplied to the engine.

With particular reference to Fig. 5, a second embodiment of the dual carburetor control system is disclosed, wherein the carburetor 13 has suction responsive motor '75 for actuating its secondary throttle valves, and the carburetor 14 has a suction responsive motor '76. Both motors 75 and 76 are identical with the suction motor disclosed in Figs. 3 and 4 and described hereinbefore. Thus, the suction motor 76 includes a diaphragm positioned rod 54, which is connected to lever extension 43 of an arm 46 attached to the secondary throttle valve shaft 42. The arm 46 includes an extension 50 carrying a link 70 to which one end of a return spring 68 is con nccted. The other end of the return spring 68 is connected to a bracket 66 carried by the diaphragm housing 58. In this embodiment, the vacuum side of the motor 75 is connected by the conduit 71 to the main venturi 19 of the primary induction passages 15 in the carburetor 13. The vacuum chamber of the motor 76 is connected by a conduit 72 with the conduit '71. Hence, both motors 75 and 76 respond to the vacuum at the main venturi in the primary induction passages of the rear carburetor, and when this vacuum reaches a predetermined value due to opening of the primary throttle valves, the motors 75 and 76 will be simultaneously actuated to open their respective secondary throttle valves.

With reference to Fig. 6, a third embodiment is disclosed wherein carburetors 13 and 14 have secondary throttle valve actuating motors 75 and 76 connected to the main venturi of the primary induction passages of the carburetor 13 in a manner identical with the embodiment disclosed in Fig. 5. However, in Fig. 6, the secondary throttle valve arms 45 and 46 are also mechanically interconnected by the link 51. Hence, operation of the Fig. 6 embodiment is the same as that of the Fig. 5 embodiment, except for the fact that the secondary throttle valves of both carburetors are mechanically synchronized, as well as being actuated by motors controlled by the same vacuum source.

With reference to Fig. 7, a fourth embodiment is disclosed wherein the carburetors 13 and 14 have independent secondary throttle valve actuating motors 75 and 76. However, the motor 75 responds to the vacuum at the main venturi 19 of the primary induction passages 15 of the carburetor 13, while the motor 76 responds to the vacuum at the main venturi 20 in the main induction passages 16 of the carburetor 14. In order to assure synchronized movement of the secondary throttle valves of both carburetors, the actuating arms 45 and 46 for the secondary throttle valves of both carburetors are interconnected by the link 51. Operation of the Fig. 7 embodiment results in synchronous movement of the secondary throttle valves of both carburetors due to the mechanical interconnection therebetween even though one of the motors 75 or 76 may respond to its vacuum source before the other one.

From the foregoing, it is apparent that the present invention provides a dual carburetor control system Wherein the secondary throttle valves of two carburetors are operated simultaneously irrespective of whether or not they are controlled by a single motor, or by a pair of motors that respond to vacuum of the same source or difierent sources. Moreover, the unique variable lever arm between the return springs and the secondary throttle valves assures that they will remain in the wide open position irrespective of vacuum fluctuations in the primary induction passages when the primary throttle valves are moved to the fully open position.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. A pair of multibarrel carburetors for supplying fuel mixture to an internal combustion engine, each carburetor having a set of primary induction passages and a set of secondary induction passages, manually controlled throttle valves in said primary induction passages for regulating the discharge of fuel mixture therefrom, means interconnecting said primary throttle valves for concurrent manual operation, secondary throttle valves in said secondary in duction passages for regulating the discharge of fuel mixture therefrom, vacuum responsive means operatively connected to the secondary throttle valves, conduit means connecting each vacuum responsive means respectively to each of said primary induction passages, and a mechanical connection between the secondary throttle valves of each carburetor whereby the vacuum forces in the respective primary induction passages are averaged for efiecting synchronized movement of said secondary throttle valves.

2. A pair of longitudinally spaced multibarrel carburetors for supplying fuel mixture to an internal combustion engine, each carburetor having a primary induction passage and a secondary induction passage, a throttle valve in each of said induction passages, means interconnecting said primary throttle valves for concurrent manual operation, arms operatively connected respectively to each of said secondary throttle valves, each of said arms having a pair of lever extensions, a vacuum responsive member mounted on each of said carburetors, means operatively connecting each vacuum responsive member and one of said lever extensions, resilient means extending from a point adjacent each vacuum responsive member to the other lever extension of each lever and opposing movement of said vacuum responsive member, the construction and arrangement being such that the efiective length of the lever extension to which each resilient means is connected decreases upon movement of each secondary throttle valve from a closed to a fully opened position, and means interconnecting corresponding extensions of the secondary throttle actuating levers for each carburetor to insure synchronized actuation of said secondary throttles.

References Cited in the file of this patent UNITED STATES PATENTS 1,920,174 Harris Aug. 1, 1933 2,420,925 Wirth May 20, 1947 2,640,472 Bicknell June 2, 1953 2,725,859 Turlay Dec. 6, 1955 

